Effect of compatibilizing agents on the physical properties of iPP/HDPE organoclay blends

Blends of isotactic polypropylene (iPP) and high density polyethylene (HDPE), with and without compatibilizers and with different organoclay amounts (1%, 3%, and 5%), were systematically investigated to assess the effect of the additives on the crystallinity of the blends, as well as the correlation between the microhardness, H and the Young's modulus E. The compatibilizers used were: maleic anhydride grafted styrene ethylene butadiene styrene (SEBS-g-MAH), maleic anhydride grafted polyethylene (PE-g-MAH), maleic anhydride grafted polypropylene (PP-g-MAH), ethylene propylene diene monomer (EPDM), and maleic anhydride grafted EPDM (EPDM-g-MAH). The thermal properties and crystallization behavior were determined by differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Macro- and micromechanical properties were also investigated. The results obtained showed that the addition of clay slightly increases the crystallinity alpha(WAXS) of the blends. However, the hardness H decreases enormously only by adding 1 wt% of clay. With higher clay amounts, H increases again. The relationship between the Young's modulus E and the hardness H for all the studied blends was found to be somewhat higher than the one obtained for polyethylene (PE) samples with different morphologies.